1. Field of the Invention
The present invention relates to an angiopathy diagnosing apparatus for diagnosing an angiopathy of a living subject, such as arteriosclerosis or arteriostenosis.
2. Related Art Statement
It is practiced to obtain, for diagnosing an angiopathy such as arteriosclerosis, arteriostenosis, aneurysm, or dissecting aneurysm, pulse-wave-propagation-velocity-related information that is related to a velocity at which a pulse wave propagates through an artery between two prescribed portions of a living subject; such as pulse-wave propagation velocity itself or pulse-wave propagation time. Since, for example, pulse-wave propagation velocity increases as arteriosclerosis advances, and conversely decreases as arteriostenosis advances, it is possible to diagnose those sorts of angiopathy based on the pulse-wave propagation velocity.
The pulse-wave-propagation-velocity-related information is also obtained for evaluating a therapeutic effect of an administered drug against arteriosclerosis or arteriostenosis. A device for obtaining pulse-wave-propagation-velocity-related information costs low, and enjoys an advantage that it can be easily used to obtain the information. Thus, this device is widely used.
Meanwhile, it is known that pulse-wave-propagation-velocity-related information is influenced by blood pressure of a living subject. Pulse-wave propagation velocity as a sort of pulse-wave-propagation-velocity-related information increases as subject's blood pressure increases, i.e., the former decreases as the latter decreases. Therefore, in order to accurately diagnose angiopathy based on pulse-wave-propagation-velocity-related information, it is needed to obtain the information when the subject shows a standard blood-pressure value. However, it is difficult to obtain, from the subject, every piece of pulse-wave-propagation-velocity-related information when the subject has the standard blood pressure. Hence, usually, it is practiced to measure, at a time of obtaining pulse-wave-propagation-velocity-related information, a blood pressure and make a rough diagnosis based on both the information and the blood pressure.
In addition, an MRI device (a magnetic-resonance imaging device) or a CT device (a computerized-tomography device) such as an X-ray CT device is known as a device capable of diagnosing angiopathy with high accuracy. Thus, if a patient is suspected of angiopathy, based on pulse-wave-propagation-velocity-related information, it is a common practice to make a final diagnosis using a CT device. However, since the accuracy of the diagnosis based on the pulse-wave-propagation-velocity-related information is not sufficiently high, a patient who, in fact, is free of angiopathy may be suspected of the disease based on the information, i.e., may be erroneously judged as needing a diagnosis using a CT device. On the other hand, each CT device is very expensive and accordingly a sufficient number of CT devices cannot be purchased. Thus, in many cases, patients must wait for their turns when they are judged as needing the CT inspection.
In addition, it is known that an upper-and-lower-limb blood-pressure measuring device can be used as a device capable of diagnosing arteriostenosis. For example, this device is disclosed in Japanese Patent No. 3,027,750 or its corresponding U.S. patent application Ser. No. 09/559,827. This upper-and-lower-limb blood-pressure measuring device includes two cuffs adapted to be worn on a superior limb (e.g., an upper arm) and an inferior limb (e.g., an ankle) of a living subject, respectively, measures superior-limb and inferior-limb blood-pressure values using the two cuffs, determines an index value by dividing the measured inferior-limb blood-pressure value by the measured superior-limb blood-pressure value, and diagnoses arteriostenosis based on the determined index value. However, the upper-and-lower-limb blood-pressure measuring device cannot diagnose arteriostenosis on the other body portions than the inferior limbs. In addition, this device cannot sufficiently accurately measure the inferior-limb blood-pressure values, and accordingly the reliability of the index values determined by the device is not sufficiently high. Moreover, this device needs a considerably long time to measure the blood-pressure values.